Cimetidine and lansoprazole have certain differences in the mechanism of action, contraindications, adverse reactions and other aspects. 1. Mechanism of action: cimetidine belongs to the H2 receptor antagonist, can block the H2 receptor of the gastric wall cells, and play a role in inhibiting the secretion of nocturnal gastric acid and basal gastric acid; lansoprazole belongs to the proton pump inhibitor, which is able to enter into the cells of the gastric wall, and combine with the H+-K+-ATPase, to inhibit the secretion of gastric acid, and is the strongest class of drugs to inhibit the secretion of gastric acid. 2. Contraindications: Cimetidine should not be used in people who are allergic to cimetidine; Lansoprazole should not be used in people who are allergic to Lansoprazole, have difficulty or pain in swallowing, or vomit with blood. 3. Adverse reactions: the adverse reactions of cimetidine include diarrhea, abdominal distension, nausea, chills, fever, rash, palpitations, etc.; the adverse reactions of lansoprazole include diarrhea, dry mouth, lack of appetite, headache, dizziness, rash, urticaria, etc.. Patients who require treatment with cimetidine or lansoprazole are advised to use the medication under medical supervision.